Memory Channel Storage is exactly what it sounds like, non-volatile flash storage that is placed into DIMM slots to take advantage of the low latency connection between the CPU and more traditional DIMMs. This may not help gamers to rack up higher scores but for server applications which have large queue depths resulting in very large IOPS. This setup also allows for workload to be shared across memory channels, as opposed to a PCIe solution which is only able to connect to the lanes accessible to that particular slot. There is a link to the white paper on The Register for those who wish to delve deeper.

"Diablo provides Memory Channel Storage (MCS) technology to SanDisk’s subsidiary SMART Storage. It’s OEMed on to Supermicro and also IBM (soon to be Lenovo) for its x86 servers as ULLtraDIMM technology."